1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having a silicide thin film that is made thermally stable by treating a surface of a Si containing substrate using argon plasma and a method of manufacturing the same.
2. Description of the Related Art
The rapid development of manufacturing techniques for silicon devices has resulted in the attainment of submicron devices. Accordingly, contact resistance and sheet resistance increase due to the minuteness of regions for forming contacts of a gate and source/drain. This phenomenon resulted in a major reduction of operation speed of a silicon device since an increase in RC delay occurs.
To solve this problem, sheet resistance and contact resistance have been reduced by forming a silicide, which is a stable metal compound formed by a reaction between Si and a metal, in contact regions such as a gate and a source/drain. Also, a self-aligned silicide (salicide) process is now used in device manufacturing processes of next generation combined-devices by coupling a high performance LOGIC device, a logic, and a dynamic random access memory (DRAM).
Silicides commonly used for manufacturing silicon devices are TiSi2 and CoSi2. These two kinds of silicides have low specific resistances suitable for the operation of a device, however, according to the disclosures of J. A. Kittle et al. published in the Digest of Technical Papers of the symposium VLSI Technology, pp 14, 1996 and J. B. Lasky et al. published in the IEEE Trans. Electron Devices, 38, pp 262, 1991, the TiSi2 has serious problems such as a difficulty of phase transform C-49 TiSi2, which has a high specific resistance, to C-54 TiSi2, which has a low specific resistance, the occurrences of a narrow line effect, in which specific resistance increase due to a reduction of a line width, and a bridge effect, which can be an electrical short between isolated devices. Also, according to the disclosures of D. K. Sohn et al., published in J. Electrochem. Soc. 147, pp 373, 2000 and E. G. Colgan et al., published in Mater. Sci. Eng. R. 16, pp 43, 1996, even though CoSi2 has advantages over TiSi2, there is a possibility of generating a CoSi2spike since Co reacts with Si fiercely and it is very difficult to form CoSi2 in a shallow junction with a low junction leakage current since the amount of silicon required for forming CoSi2 is greater than for other silicides.
Recently, according to the disclosure of F. Deng et al., published in J. Appl. Phys., 81, pp 8047, 1997, nickel mono-silicide (NiSi) which overcomes the problems of TiSi2 and CoSi2, has been proposed and applied to manufacture a next generation high performance silicon device.
Meanwhile, according to the disclosures of T. Morimoto et al., published in Tech. Dig. Int. Electron Devices Meet., pp 653, 1991 and T. Hou et al., published in IEEE Electron Device Letters, 20, pp 572, 1999, a NiSi thin film that has a low specific resistance of 14 μΩ·cm can be obtained using a single heat treatment, and the obtained NiSi thin film has no narrow line effect or bridge effect that occurs in TiSi2. Moreover, the amount of Si required to form the NiSi with a predetermined thickness is much less than for other suicides, especially, CoSi2. Therefore, NiSi is a suitable silicide to be applied to a next generation Si device having a shallow junction.
When practically applying NiSi to a Si device, NiSi drastically increases the sheet resistance as the heat treatment temperature increases, that is, thermal stability is reduced. These problems are mainly caused by the oxidation of the NiSi thin film due to contamination of oxygen, as disclosure in T. Ohguro et al., published in Tech. Dig. Int. Electron Devices Meet., pp 453, 1995. Also, if the NiSi thin film is oxidized, severe undulation is generated at an interface between NiSi and a Si substrate and the surface morphology of the NiSi thin film severely degrades.
To solve these problems, a TiN capping layer is widely used. As disclosed in Japanese Patent Laid-Open Publication 7-38104, a diffusion barrier layer is formed to prevent oxygen contamination by forming a TiN capping layer on Ni. However, while oxygen contamination can be effectively prevented when the capping layer is used, it is difficult to apply a capping layer to a shallow junction due to a large undulation at an interface between the NiSi thin film and a Si substrate, as disclosed in T. Ohguro et al., published in Tech. Dig. Int. Electron Devices Meet., pp 453, 1995.
Another method of reducing oxidation of the NiSi thin film by oxygen contamination is disclosed in U.S. Pat. No. 5,840,626. This is a method of forming NiSi by heat treating a Ni thin film after depositing Ni on Si substrate with a small amount of nitrogen. When NiSi is formed by this method, nitridation of a surface of the NiSi thin film occurs, and the nitridation of the surface of the NiSi thin film effectively prevents the oxidation of the NiSi thin film. However, this method has a drawback in that a large amount of nitrogen must be added to the Ni thin film since Ni does not readily reacts with nitrogen, as indicated by U.S. Pat. No. 6,410,427. Also, this method has a drawback in that the temperature required for heat treatment when forming a NiSi thin film having low resistance increases as the concentration of nitrogen increases.